This invention relates to a submersible robotic apparatus for cleaning water tanks, reservoirs, swimming pools or the like, and more particularly to means for controlling the direction of travel of the apparatus along the bottom of the tank or pool to be cleaned.
Self-contained electrically powered robotic devices for cleaning water tanks, reservoirs or more particularly, swimming pools are well known. These devices generally comprise a housing, a removable filter bag disposed within the housing for removing and retaining debris from the water, a pump for drawing water through the filter bag, and two parallel motor-driven cylindrical brushes disposed at both ends of the housing for propelling the cleaner along and sweeping the bottom surface of the pool. Tank or caterpillar type tracks usually extend between the cylindrical brushes on both sides of the housing and assist in moving the cleaner along the surface to be cleaned by providing increased traction. The pump which draws the water through the filter bag provides a downward thrust to maintain the cleaner in contact with the internal surface of the pool being cleaned. Solid State timers, switches and microprocessors are provided to reverse the direction of the drive motors at predetermined or preprogrammed time intervals and to automatically stop the device after it has completed a pretimed cleaning cycle.
Unfortunately, merely reversing a drive motor causes the cleaning device to move forward and backward along the same path and thus does not effectively cover the entire surface to be cleaned. This deficiency is overcome in those pool cleaners which are adapted to climb the walls of the pool by means of a floatation device which provides an upward bias at an angle to the direction of movement of the cleaner, thus causing the pool cleaner to veer off in a slightly different direction as it climbs the wall of the pool. When the drive motor is then reversed, the pool cleaner traverses a path which differs from the path previously traveled. In this manner, over a period of time, a substantial portion of the bottom and the walls are covered by the cleaner.
In large public swimming pools and industrial water tanks or reservoirs it is often impractical for the cleaning device to be adapted to climb the walls due to the time constraints involved in cleaning large bottom surface areas or the steepness or irregularity of the walls. Thus, a problem arose in developing means for directing the path of travel of cleaners whose direction could not be controlled by a biased float means. To solve this problem various complex devices were developed to steer the cleaning apparatus to travel along preprogrammed paths. Such devices include multiple wheels which are individually motor-driven and which are activated and deactivated according to the program and complex clutch devices connected to a single motor and adapted to engage and disengage various drive wheels according to the program. These devices also include either mechanical or electronic sensing devices, such as ultrasound, laser or infrared, which are adapted to reverse the drive motors and when the device comes in contact with, or nears, the walls of a pool or tank or other obstacle. Unfortunately, devices of this type are expensive and unduly complex and because of such complexity are often unreliable.